WAN: flush tx_queue in hdlc_ppp to prevent panic on rmmod hw_driver.

[ Upstream commit 31f634a63de7068c6a5dcb0d7b09b24b61a5cf88 ]

tx_queue is used as a temporary queue when not allowed to queue skb
directly to the hw device driver (which may sleep). Most paths flush
it before returning, but ppp_start() currently cannot. Make sure we
don't leave skbs pointing to a non-existent device.

Thanks to Michael Barkowski for reporting this problem.

Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/net/wan/hdlc_ppp.c b/drivers/net/wan/hdlc_ppp.c
index b9b9d6b01c0b..941f053e650e 100644
--- a/drivers/net/wan/hdlc_ppp.c
+++ b/drivers/net/wan/hdlc_ppp.c
@@ -628,9 +628,15 @@ static void ppp_stop(struct net_device *dev)
         ppp_cp_event(dev, PID_LCP, STOP, 0, 0, 0, NULL);
 }
 
+static void ppp_close(struct net_device *dev)
+{
+        ppp_tx_flush();
+}
+
 static struct hdlc_proto proto = {
         .start          = ppp_start,
         .stop           = ppp_stop,
+        .close          = ppp_close,
         .type_trans     = ppp_type_trans,
         .ioctl          = ppp_ioctl,
         .netif_rx       = ppp_rx,